The technical field of the invention concerns the detection and locating of defects visible to the human eye over large surfaces, such as the outer surfaces of large objects, for example aircraft, ships, trains, motor vehicles, buildings or engineering structures. In general, the term “object” shall be understood herein as a tangible thing that can be perceived through sight and touch, made by man and intended for a specific use. Large objects, i.e. objects whose dimensions, bulk and/or weight do not allow them to be carried by a person, generally have hard-to-reach surfaces, for example portions of buildings or engineering structures that are situated at height, the outer hull of large ships, the structure of an oil platform or the upper part of train sections or aircraft fuselages and wings. Detecting and locating defects visible to the eye on this type of large object therefore presents several problems, in particular problems concerning obtaining visual access to the surfaces, detecting defects and locating defects in a coordinate system related to the object. The defects to be detected are, for example, impacts caused by a lightning strike, hail, birds or debris, or corrosion, erosion, paint running or crack defects, etc.
Defects are detected and located by inspecting the surfaces of the objects. A plurality of inspection systems and methods have been proposed in order to overcome these problems.
In general, inspections are currently performed by human operators. Specific equipment is used to provide said operators with visual access to the surfaces, for example the use of cherry pickers or scaffolding, etc. For more hard-to-reach surfaces, the operator may, for example, also be required to use binoculars or equivalent optical means.
Human operators are specially trained to detect defects by inspecting surfaces. The detection of these defects is therefore reliant on the experience and perception of the operators. Once a defect has been detected, the operator is responsible for locating said defects, i.e. for recording the absolute location of the detected defect, or more commonly the location thereof relative to one or more points of reference present on the object. These points of reference can be, for example depending on the type of object inspected, windows or portholes, structural elements such as cables, posts, columns, frames, spars, stringers, textual markers, or specific distinctive elements, etc. A defect is thus located by firstly determining at least one point of reference, and then by measuring the position of the defect relative to each reference point.
However, these inspections performed by one or more human operators have several drawbacks.
The installation of specific equipment such as scaffolding in order to obtain visual access to the surfaces is time-consuming and expensive, and does not systematically provide easy access to the surfaces to be inspected. The use of binoculars or equivalent optical means in order to overcome this drawback is unsatisfactory as this reduces the efficiency of the inspection. Moreover, the use of specific equipment generally increases safety risks for the operator, in particular falling or crushing risks, or any other risk brought about by the use of specific equipment such as cherry pickers or scaffolding. The specific equipment also generates risks for the object, in particular collision risks capable of causing deterioration. Depending on the fragility of the object, this deterioration could have significant repercussions, such as immobilisation or grounding (for vehicles and aircraft), expensive repairs or the permanent suspension of operation. These drawbacks and risks are all the more important as the number of operators increases.
Furthermore, the detection performed by the operators is imperfect, as an operator could forget to visually scan a portion of the surface, in particular if the surface is hard to reach. The operator could also treat the surfaces unequally depending on whether they are easy to reach. Finally, the subjectivity of each operator can result in a different classification of the elements perceived (for example between major defects, minor defects, normal wear or marks), which could lead the operator to ignore or only belatedly detect certain defects. Moreover, the operators must be specially trained for the inspection, which reduces the number of operators capable of performing the inspection and requires additional management with regard to the availability and cost of a team of trained operators.
Finally, the locating techniques can produce errors, in particular with regard to the selection and identification of the points of reference, for example if this selection requires a high number of repetitive elements to be counted (portholes, windows, columns, etc.), which can be added to the conventional errors made when measuring from one or more points of reference.
The inspections performed with the existing systems and methods are also subjected to an additional speed problem. Current inspections generally require the operation of the object to be suspended over a long period of time. In order to improve inspection speed, the number of operators responsible for conducting this inspection must be increased, which in particular generates additional costs and increases the risks described hereinabove.
Solutions have been proposed to overcome these drawbacks. For example, the use of a rolling robot equipped with optical means designed to better detect and locate defects, and thus reduce the subjectivity of the detection and location determination errors. However, the problem of acquiring visual access remains and the method is slow, insofar as an operator is required to intervene for each detection. Another solution involves placing the object to be inspected in a hangar equipped with a plurality of cameras capable of inspecting the surface of the object. This system however cannot be used for buildings and engineering structures, cannot be displaced and is not modular. In particular, such a system requires the object to be inspected, for example an aircraft, to be transported to the hangar, which is expensive and complex.
The inventors have therefore sought to propose an inspection system and method that overcomes at least some of the drawbacks of known systems and methods.